Pumps are used at the industrial level in many different industries for a variety of purposes. In the petroleum industry for example a large number of pumps of different sizes is used to perform a large number of pumping functions. In heavy industry it is not uncommon for pumps to fail because of contaminants contained within the pumpage or within the pump itself. Pumps are provided with a myriad of seals, bushings and packing arrangements to protect the components thereof from contamination and subsequent wear or damage.
Attempts have been made in the past to devise pump accessories that will reduce the damage due to such contaminants, one successful accessory being the SpiralTrac™ seal protector manufactured by EnviroSeal Engineering Products Ltd. of Nova Scotia, Canada. This device may be considered to be an annular bushing that is placed at the entrance to a seal cavity of a pump, the cavity being defined by a portion of the pump housing, a shaft that extends through the cavity, and means for sealing the cavity itself. The sealing means may take the form of a mechanical seal positioned at one (the distal) end of the cavity) or it may take the form of packing material that fills the cavity. In either case the SpiralTrac™ bushing is positioned at the proximal end of the cavity. The bushing includes a tapered central bore which has a spiral groove formed in its wall and that leads from adjacent the outer surface of the bushing towards the cavity entrance. The spiral groove decreases, generally, in diameter down to the innermost diameter of the bushing which defines a small annular gap around the shaft. As the shaft rotates any particulate material that enters the seal cavity during operation of the pump will be centrifugally forced into the spiral groove and will flow therealong towards the gap by the shaft. The particulate material will be forced outwardly through the gap to the exterior of the seal cavity. This bushing is disclosed and claimed in U.S. Pat. No. 5,553,868 of Sep. 10, 1996 and in Australian Patent No. 688,977 of Oct. 18, 1995 as well as in Canadian and European applications.
The bushing as taught in the aforementioned US patent is particularly advantageous with seal cavities that include a mechanical seal at the distal end thereof. The applicant herein also produces seal bushings which are especially adapted for use with packing material that in essence fills the seal cavity, which bushings operate on the same principle but require physical modifications to the design in order to accommodate the packing material. For example, a bushing for a packing environment requires a generally flat annular distal end face against which the packing material can abut, while such a flat face is not required or desired for a non-packing environment.
In some instances pump manufacturers or operators may wish to convert their pumps which use mechanical seals at the distal end of a seal cavity to pumps which use packing material within the seal cavity, or vice versa. If the pump is already using a SpiralTrac™ seal bushing for a mechanical seal cavity it would be necessary to discard that bushing and to replace it with one that is adapted for use with packing material. This would entail a not insubstantial expense, especially since the SpiralTrac™ bushing is considered to have a considerably longer life than conventional seal cavity bushings. There is therefore a need for a bushing arrangement that can be used with either a mechanical seal cavity or with a packing material cavity without considerable additional expense or effort on the part of the manufacturer or the operator.